JPS61154128A - Exposure unit - Google Patents

Abstract

PURPOSE:To minimize the variability of exposure, by comparing a detected exposure with a predetermined exposure and controlling the exposure with a predetermined number of pulses. CONSTITUTION:A mirror 4 is arranged in the light path of an illuminating optical system 2, and a ultraviolet photo sensor 5 is arranged in the light path of the light reflected by the mirror 4. Output of the photosensor 5 is inputted to a lightquantity integrating circuit 6 to which the sensitivity of photo resist has been previously inputted, and is further inputted to a CPU 7 through a comparator circuit 9 for comparating a proper exposure and an integrated exposure. The CPU 7 calculates a number of pulses required for exposing the photo resist material on a wafer W to light. A laser output control unit 8 drives an excimer laser source 1 based on the calculation by the CPU 7 so that the pattern of a mask M is transferred on the wafer with the irradiation of light whose output is controlled by the unit 8 as required.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to an exposure apparatus, and in particular to a semiconductor exposure apparatus. With the development of new lenses, etc., the field is expanding further. When using such exposure equipment to transfer and print a circuit pattern on a mask or reticle onto a wafer, the resolution line width of the circuit pattern printed on the wafer is proportional to the wavelength of the light source, so in recent years far-ultraviolet However, these light sources have low output in the deep UV region, and the photoresist material coated on the wafer has low photosensitivity, so the exposure time is long. The throughput becomes smaller.

On the other hand, in recent years, it has been discovered that excimer lasers, high-output light sources in the AEEP UV range, can be used as powerful means for exposure equipment. e
-Unlike the Hg lamp, it uses a pulse oscillation method, and therefore cannot use the conventional analog exposure control method, that is, the method of controlling the time set by a timer using a shutter.Furthermore, in the case of an excimer laser, 1
It is known that variations in pulse output reach ±5% or more, so it is necessary to suppress variations in exposure amount to a small level.

(Objective) An object of the present invention is to provide an exposure apparatus that performs preferable exposure control in view of the pulsed light emission characteristic of excimer lasers.

In addition, the present invention is based on the actual exposure amount and the predetermined exposure amount (appropriate exposure amount).
An object of the present invention is to provide an exposure apparatus in which the number of pulses is controlled so as to suppress the difference in the number of pulses to a small value.

Furthermore, the present invention also controls the pulse output to further reduce the difference between the actual exposure amount and the predetermined exposure amount (appropriate exposure amount).
DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiments) Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, an excimer laser light source 1 is, for example, Kr.
F'p Xe01 is sealed and is a light source that emits pulsed laser light.
In FIG. 2, the illumination optical system 2 includes a beam shaping optical system 21 such as a toric lens, and an optical integrator such as a fly's eye lens. 22, a collimator lens 23, and a mirror 24, these optical systems 21.22.23
is made of K, quartz (S10z) so that light in the far ultraviolet region can pass through.
), Tatamikata (CaF 2 ), and other materials.

The beam shaping optical system 21 is for shaping the light of a commercially available excimer laser light source into a desired shape, for example, a square, since the light is usually rectangular. It is for the purpose of

Returning to FIG. 1, a mask M or a reticle on which an integrated circuit pattern is formed is arranged along the optical path of the illumination optical system 2, and a projection optical system 3 and a wafer W are also arranged. Both the projection optical system 3 and the illumination optical system 2 and imaging system can be used.

Illumination optical system 2. A mirror 4 is disposed on the optical path, and an ultraviolet photo sensor 5 is disposed on the optical path reflected by the mirror 4. This photosenna 5 may be placed near the laser light source 1 or within the optical path from the light source 1 to the wafer W. 7 The output of the photo sensor 5 is input to a light amount loading circuit 6 into which the sensitivity of the photoresist is input in advance, and is further input to a central processing unit (CPU) 7 via a comparison circuit 9 that compares the appropriate exposure amount and the cumulative exposure amount. Then, the number of pulses required to expose seven photoresist materials on the wafer W is calculated. The laser output control section 8 drives the excimer laser light source 1 based on the calculation result of the CPU 7, and the pattern of the mask M is exposed on the wafer WK with the light whose output is controlled as necessary.

In addition, if necessary, the lighting system efficiency control section 10'
The efficiency of the illumination system (for example, the diameter of the luminous flux and the amount of light) is controlled based on the calculation result of U7.

Note that a laser output control section 8 is used to control the output of the pulsed light.
Either or both of the f illumination system efficiency control sections 10 can be used.

Now, since the excimer laser has a high output, one pulse of exposure may be sufficient, but it is known that the output variation between each pulse of an excimer laser reaches ±5% or more, and therefore the stepper laser In several types of processes in which the most minute processing is performed, such as in the case of exposure with only one pulse per shot, this amount of variation can also become a problem. Therefore, since the output of the excimer laser can be adjusted as described above, a stable exposure amount can be obtained by lowering the output and controlling the exposure to be completed with a plurality of pulses per shot.

In other words, according to the flowchart shown in Fig. 3, the exposure is performed with KW pulses as shown in Fig. 4, the amount of exposure that has already been exposed is monitored with the integrating exposure meter, and the degree of under or over exposure is minimized by comparing it with the appropriate exposure amount. Exposure is further given for a predetermined number of pulses (for example, 1 pulse) so as to achieve this.

In this case, the cumulative exposure amount will generally not match the appropriate exposure amount due to the final pulse exposure and will be under or over, but compared to the case of 1 pulse per shot, the difference between the actual exposure amount and the appropriate exposure amount can be kept small. be able to.

Furthermore, as shown in Fig. 5, if the pulse output is further reduced and the number of pulses per shot is increased, even if there is a variation in the exposure amount of the final pulse, the absolute value is small, giving an exposure closer to the appropriate exposure amount. That will happen.

As mentioned above, the pulse output may be reduced by reducing the output of the laser light source itself, or by installing an ND filter or the like in the optical path after the laser light source, or reducing the diameter of the illumination beam to improve the efficiency of the illumination system. The output may be lowered by changing . Note that priority may be given to adjusting the output of the laser light source itself, and the deficiency may be compensated for by adjusting the efficiency of the illumination system, such as adjusting the illumination beam diameter 9 light quantity.

In the above example, the expected output for each pulse is constant, but at least one pulse may be compared with other pulses to have a different expected output.

For example, as shown in Figure 6, only the final pulse may be compared with other pulses to determine the expected output. In this case, the expected output of the final pulse may be smaller or smaller than the expected output of the other pulses. be made larger.

This K allows the cumulative exposure amount to match the appropriate exposure amount.

Further, as shown in FIG. 7, the expected output may be made different for a plurality of consecutive pulses up to the final pulse compared to other pulses.

In this case, for the appropriate exposure amount HaK, the first %1 pulse is output E1 and the next %1 pulse is output E2 + the final ? &3 pulse is performed with output E3, go = 31"1 +4zKz +f&sEs where E□=, = α1E0.E2 = α2E@+L = αsFa.

Then, 1%1α1+n2α2+3α3=1. However, if α1°α2Iα3 is adjusted so that n s + n 2 + jl a is as small as possible, the exposure time can be made as small as possible.

Now, since the repetition frequency of the light emission of the excimer laser is very high at 200 Hz to 300 Hz for commercially available lasers, the throughput is improved compared to the conventional aligner even in this manner. For example, even if exposure is performed with an average of 10 pulses per shot, and the number of pulses varies between 9 and 11 due to variations in pulse output, the exposure time will be 0.
．． All will be within 0.04 to 0.05 seconds. Considering that the exposure time of current steppers takes around 0.3 seconds per shot, this value is an order of magnitude smaller, and the exposure amount can be stabilized and the throughput can be improved. Even if exposure is performed with 20 pulses, the exposure time is completed in about 0.1 seconds, which is a clear improvement over the conventional method.

Here, one shot refers to the exposure sufficient to expose the entire wafer, or one shot in the case of the so-called step-and-repeat method in which each chip on the wafer is exposed. In the case of slit exposure, the exposure amount is sufficient to expose one slit width.

Further, the present invention can be applied not only to a projection exposure apparatus using a lens including a stepper as shown in FIG. 1, but also to a mirror projection type, contact or gloximity type exposure apparatus.

As described above, according to the present invention, it is possible to stably obtain an appropriate exposure amount in a semiconductor exposure apparatus using a pulsed laser such as an excimer laser, despite large variations in the exposure amount per pulse.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an exposure apparatus for a reduction projection plate, a so-called stepper, according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an illumination optical system 2 shown in FIG. 1, and FIG. 3 is an exposure 4 to 7 are diagrams showing each embodiment of pulse number control. In the figure, 1 is the excimer laser 5, the photosensor 6 is the light amount integration circuit 7 is the CPU, and 8 is the laser output control section. 9 is a comparison circuit

Claims (9)

[Claims] (1) means for generating a pulsed laser beam with an exposure amount smaller than a predetermined exposure amount; an exposure amount detection means for integrating and detecting the exposure amount of the pulsed laser beam; and the exposure amount detection means. An exposure apparatus comprising means for comparing the detected exposure amount with the predetermined exposure amount to control further exposure of a predetermined number of pulses. (2) The exposure apparatus according to claim (1), wherein the expected output of each pulse is constant. (3) The exposure apparatus according to claim (1), wherein the means for generating the pulsed laser light is an excimer laser. (4) means for generating pulsed laser light with an exposure amount smaller than a predetermined exposure amount; pulse output variable means for varying the pulse output; and integrating and detecting the exposure amount by the pulsed laser light. An exposure apparatus comprising: an exposure amount detection means; and a means for comparing the exposure amount detected by the exposure amount detection means with the predetermined exposure amount to control further exposure of a predetermined number of pulses. (5) The exposure apparatus according to claim (4), wherein the expected output of each pulse is constant. (6) The exposure apparatus according to claim (4), wherein at least one pulse to be exposed has a different expected output from other pulses. (7) The exposure apparatus according to claim (6), in which only the final pulse has a different expected output from other pulses. (8) Claim No. 6 in which a plurality of consecutive pulses leading to the final pulse have different expected outputs from other pulses.
) Exposure device described in section 2. (9) The exposure apparatus according to claim (4), wherein the means for generating pulsed laser light is an excimer laser.